Internal loop reactor and Oxo process using same

ABSTRACT

The invention relates to improvements in internal loop reactors. The reactor of the invention is characterized by a plurality of cooling tubes which form the annulus between the riser and the downcomer path of said internal loop reactor. The reactor also provides improvements in hydroformylation reactions using the improved reactor.

FIELD OF THE INVENTION

The invention relates to improvements in reactors, particularly internalloop reactors. In embodiments, there are also improvements inheterogeneous (gas/liquid phase) exothermic reactions, particularlyhydroformylation reactions, using the improved reactor.

BACKGROUND OF THE INVENTION

The hydroformylation reaction, also known as the Oxo Reaction or OxoProcess, consists in reacting a synthesis gas made up of a mixture ofcarbon monoxide and hydrogen and at least one C_(n)H_(2n) olefin so asto obtain a mixture of aldehydes and primary alcohols containing n+1carbon atoms. The reaction is generally catalyzed with carbonyls oftransition metals such as cobalt. This type of reaction is described indetail in patents too numerous to recite. It is commercially highlyimportant, producing products that find uses in plastics, soaps,lubricants, and other products

The reactors in which the Oxo Process is carried out can be identical ordifferent in all process stages. Examples of types of reactor which canbe used are bubble columns, loop reactors, jet nozzle reactors, stirredreactors and tube reactors, some of which can be cascaded and/orprovided with internals.

As part of the reactor of the “loop” type the liquid phase is recycledand the gas phase is allowed to exit the reactor at the top of the loop.External loop reactors are illustrated, for instance, in U.S. Pat. No.4,312,837 (Papp et al.). The typical reactor used in Oxo is an externalloop reactor, but internal loop reactors are also used.

An example of an conventional internal loop reactor is illustrated inFIG. 1 of the present disclosure. Such a reactor is made up of at leasttwo concentric vertical tubes 1 and 2 connected to each other at theirupper and lower ends. As shown in FIG. 1, the vertical column 1 of loopreactor 4 acts as the ascending branch (“riser”) while vertical column 2act as the descending branch (“downcomer”). The vertical columns aresupplied with jacketed cooling means 3. Ascending vertical column 1 iscontinuously supplied at its base with the synthesis gas and liquidphase through inlet 5. Essentially all the synthesis gas and the excessliquid phase is evacuated at the upper connection 6, while essentiallyonly the liquid phase circulates between ascending column 1 anddescending column 2, said circulation illustrated by arrows 7. Thedifference between the specific gravities of the gas/liquid phasemixture on the one hand and the liquid phase alone on the other handresults in a difference in hydrostatic pressure between the ascendingbranch and the descending branch, thus leading to circulation of theliquid phase in the reactor.

Loop reactors of both the internal and external type are used inreactions other than the Oxo Process. They are useful particularly inexothermic and/or heterogenous (gas/liquid) reactions and have been usedfor such diverse reactions as the oxidation of p-xylene (U.S. Pat. No.4,342,876), biotechnological reactions (WO 8804317), and thepurification of water (U.S. Pat. No. 6,544,421). It is known that byvarying the geometries of the reactor, it is possible to eliminatecertain problems encountered in specific reactions. See, for instance,U.S. Pat. No. 4,312,837 (FR 2430794 A1); U.S. Pat. Nos. 4,342,876;5,277,878; 5,503,810; and 6,106,789. There is, however, no shortage ofproblems to be solved in these systems and typically solving one problemby simply varying geometries introduces at least one new problem.

One of the main problems with conventional loop reactors, is that theyare limited in size. At least in part this is simply a matter of thepractical difficulty in bending large tubes. In addition, constructionof large reactors is also made difficult because the vessels must beerected in the field by sliding internals, which must be standingvertically; otherwise, with reactor on its side, the internals will bendand warp. Furthermore, in the case of the Oxo Process, the reactiontypically occurs at very high pressures, such as 4,000 lbs/in (or about28 MPa), which further limits the size of the vessels as they are knownto be constructed in the prior art. As far as the present inventors areaware, the largest known loop reactors have a volume of about 8-12 cubicmeters.

The present inventors have discovered that by building an internal loopreactor so that the separation between the riser and downcomer portionscomprises a heat exchanger, preferably one or more cooling tubes, allowsfor all the necessary parts to be attached to a reactor head. Thisallows more convenient construction of the reactor in the field andfurthermore reactor volume can be increased considerably over prior artOxo Reactors.

SUMMARY OF THE INVENTION

The invention is directed to an internal loop reactor having a heatexchanger defining barrier between riser and downcomer sections, saidbarrier referred to herein as the draft tube. The draft tube, which inan embodiment comprises one or more cooling tubes, is preferably in anelongated annular or cylindrical shape, but may take some pattern otherthan circular pattern, e.g., a polygon pattern, or a multipointed starpattern, or an irregular pattern.

In an embodiment, the single cooling tube (or cooling annulus) orplurality of cooling tubes forming the draft tube are attached to thetop of the reactor so as to allow circulation of the liquid phase to theoutside downcomer part of the internal loop reactor. In addition, theconnection of virtually all necessary internal parts to the top of thereactor allows for ease of construction, as will become apparent in thefollowing disclosure.

In another embodiment, the plurality of cooling tubes are attached toeach other by “webs” or metal strips attached, such as by welding,between the tubes over a predetermined length, such as determined to bethe optimum for the height and position of the riser.

In a preferred embodiment the bottom portion of the reaction vessel hasa hemispherical bottom.

In yet another embodiment, lateral support for the single cooling tubeor plurality of cooling tubes is provided by at least one lateralsupport rod so as to connect one or more cooling tubes or webs to theouter vessel wall. In preferred embodiment the one or more lateralsupport rods are hinged at the vessel wall and/or at the connectingpoint of the one or more cooling tubes or webs. In another preferredembodiment the one or more lateral support rods are constructed of amaterial that allows flexibility, such as bending.

In still another embodiment, a cooling jacket is attached to the reactorshell to provide heat transfer from the reactor.

In yet still another embodiment, there is a method of constructing alarge scale internal loop reactor wherein all necessary internal partsare connected to a reactor head which can be lowered into a fixed,vertical shell reactor vessel to facilitate construction and maintenancein the field.

The invention is also directed to a chemical reaction, more preferablyan exothermic and/or heterogenous (gas/liquid phases) reaction, andstill more preferably the Oxo Process, carried out in the reactoraccording to the invention.

It is an object of the invention to facilitate ease of construction andmaintenance in the field and allow process scale-up for reactions inreactors of the loop-type.

These and other objects, features, and advantages will become apparentas reference is made to the following drawings, detailed description,preferred embodiments, examples, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, like reference numerals are used to denotelike parts throughout the several views.

FIG. 1 shows the side view of a prior art internal loop reactor.

FIG. 2A illustrates a side view of a reactor according to an embodimentof the present invention and FIG. 2B illustrates certain detailedfeatures of such a reactor.

FIG. 3 provide a side view showing certain details of embodiments of thepresent invention as it relates to the top portion of the reactor.

FIGS. 4A and 4B shows a top view and bottom view, respectively, of thearrangement of cooling tubes according to an embodiment of theinvention.

FIG. 5 illustrates the lateral support bars for the cooling tubesaccording to an embodiment of the invention.

FIG. 6 shows a bottom view of the arrangement of cooling tubes accordingto an embodiment of the invention.

DETAILED DESCRIPTION

According to the invention, an internal loop reactor is characterized bya heat exchanger, preferably comprising at least one cooling tube, andmore preferably a plurality of cooling tubes, forming the barrierbetween the riser and the downcomer path of said internal loop reactor,said barrier forming what it referred to herein as the draft tube.

As shown in a side view of an embodiment of the reactor according to theinvention provided by FIG. 2A, the internal loop reactor 8 comprises apressure vessel 20 containing a cylinder or draft tube 16 suspended fromvessel head 10 along the vessel centerline. The draft tube 16 is formedby the cooling tubes with optional connecting web or sheets andprovides, inside of draft tube 16, the riser column (which is equivalentin function to riser column 1 in FIG. 1). In a preferred embodiment, atwo-phase mixture comprising syngas and Oxo product and/or reactantsfrom the upstream reactors is fed to the bottom of the reactor throughinlet 24 and directed, such as by optional sparger 28, into the internalriser column provided by draft tube 16. At the top of the riser, gaspartially or wholly disengages from the riser outlet and exits thereactor at the top through outlet 30. Liquid, which is at least nowpartially, virtually, or completely free of gas, flows through gaps orwindows 12 and 14 in the upper portion of draft tube 16 and falls downthe annular space 18 (downcomer column) between draft tube 16 outer walland the inner wall of vessel 20, enters the riser column inside of drafttube 16 at the bottom of draft tube 16 (see also arrow 700 in FIG. 2Bindicating flow direction) to mix with the fresh feed provided throughinlet 24, setting up an internal circulation loop. (In the preferredembodiment wherein the reaction is the Oxo Reaction, it is preferredthat at least some gas goes over into the downcomer so that the reactioncontinues to some extent in downcomer column 18. By way of non-limitingexample, if the riser column contains 10% by volume gas, it may beconvenient to have the downcomer column contain 3% by volume gas in theupper portion of the downcomer. This may be achieved by properdimensions of the reactor and/or reaction variables such asconcentration of ingredients, temperature, etc.). The pressure vessel 20is preferably fitted with a hemispherical bottom 11. Conveniently, thehemispherical bottom may be removeably affixed or hinged to facilitateinspection and maintenance of the reactor. Features 34 and 36 in FIG. 2relate to the cooling medium provided to the plurality of cooling tubesand are explained in detail with reference to FIG. 3, below. Features22A, 22B, 22C, and 22D are optional thermocouples or other devices whichmay be used to monitor and/or control, such as by an operator and/orwith the aid of a computer, the temperature of the reaction/reactor.

One of the advantages of the present invention is that the scale of theOxo Reaction can be greatly increased from conventional loop reactorsused in said Reaction. In preferred embodiments, the reactor 8 may have,by way of example and not to be construed as limiting, an internalvolume on the order of 20-40 cubic meters operating with a recirculationrate of 700-900 cubic meters per hour and velocities in the riser anddowncomer of about 0.4-0.6 meters/second. In embodiments, the internaldiameter of vessel 20 can be on the order of 1 to 2 meters, and theheight of the vessel 20 (extending up to the head 34) on the order of20-30 meters. The ratio of the area of the downcomer portion to riserportion is preferably close to unity and can conveniently range from 0.5to 1.5. However, these numbers may be varied depending on the reactionand desired results and should not be taken at critical limitations.Without wishing to be bound by theory, in embodiments, such a reactor isessentially a nearly isothermal, continuous stirred tank reactor (CSTR).

The materials with which to construct the apparatus of the invention donot form a part of the present invention and the various parts may beconstructed of conventional materials, e.g., the vessel sidewall 20 inFIG. 2A may be solid alloy, carbon steel with a bonded liner, and thelike.

An essential feature of the present invention is that temperaturecontrol of the reactor is provided by the heat exchanger (e.g., coolingtube(s)) which also form an essential geometric feature of the internalloop, i.e., the riser and downcomer columns separated by the draft tubecomprising said heat exchanger. Typically the riser and downcomercolumns will be concentric tubes, which implies that, viewed from thetop, the columns comprise essentially two concentric circles, but theshapes do not have to be circular, as will become apparent in thisdetailed description. Additional temperature control may be provided byoptional cooling jacket provided against the vessel wall (not shown inFIG. 2A) as in conventional reactors, e.g., analogous to element 3 inFIG. 1.

In preferred embodiments the surface area of the heat exchanger (e.g.,one or more cooling tubes) forming the draft tube is made large enoughsuch that the reactor temperature is open loop stable such that nofeedback control is needed on the reactor temperature itself. Therecirculating cooling water (or heating water, as the case may be)temperature is the only required control system. It will be appreciatedby ordinary artisan that the heat exchange medium may be some otherfluid besides water, e.g., a hydrocarbon fluid.

FIG. 2B illustrates some details not shown in FIG. 2A. In FIG. 2B, thereare plural cooling tubes 19A, 19B, 19C etc., which together with plateor webs 41A, 41B, etc., form draft tube 16. Plates or webs 41A, 41B,etc., does not extend all the way to plate or tubesheet 32 (discussed inmore detail with respect to FIG. 3) but rather at least a portion of theplate or web 41 is omitted so as to provides at least one window orgap(s) 12, 14, etc., whereby the liquid, at least partially free of gas,flows into the downcomer 18, as illustrated by arrow 70. As shown inFIG. 2B, the gap(s) 12, 14, etc., are spaced a distance 25A from element32, with distance 25A being readily determined by one of ordinary skillin the art in possession of the present disclosure. When there areplural gaps, as shown in this embodiment (12 and 14) the gap distance25A does not need to be the same for each gap. In the embodimentillustrated in FIG. 2B, the plates or webs 41A, 41B, etc., may beextended below the bottom of the cooling tubes 19A, 19B, 19C, etc.,shown by element 410, to at least partially enclose the top of the inletprovided by element 24, discussed above with respect to FIG. 2A.However, this extension of the connective web or sheet is merelyoptional, and in a preferred embodiment the cooling tubes 19A, 19B, 19C,etc., as well as the connect webs or sheets 41A, 41B, etc., extend belowthe top of inlet 24, so that the feed entering through inlet 24 entersthe loop reactor inside the draft tube 16). Thus draft tube 16, which inthe center portion comprises heat exchanger(s) such as 19A, 19B,19C,etc., and optional plates or webs 41A, 41B, etc., may comprise only theplate or web 410 in the lower portion. The distance by which the coolingtube(s) 19A, 19B, 19C, extend beyond the plates or webs 41A, 41B, etc.,(if at all), or in the embodiment illustrated, the distance by which theplate or web 410, extends beyond the cooling tube(s), (if at all), andlikewise the distance 25B by which the inlet tube (with optionalsparger) extends up into the draft tube (if at all) may be predeterminedby one of ordinary skill in the art. Thus, in an embodiment the platesor webs 41A, 41B, etc., may stop some distance prior to the bottom orthe cooling tube(s) 19A, 19B, etc. Arrow 700 illustrates the movement ofthe liquid from the downcomer around the base of the draft tube 16formed by plate or web 410 where the liquid is mixed with the materialadded through inlet 24 in the riser portion formed by draft tube 16.

In a preferred embodiment (not visible in FIG. 2B), in the upper portionof draft tube 16, in order to increase flow from the inside riser column15 over to downcomer column 18, the draft tubes may be “dog-legged” inor out in an alternating fashion. For instance, in FIG. 2B, cooling tube19B may be dog-legged inwardly (with respect to the centerline of thedraft tube 16) while cooling tubes 19A and 19C may be dog-leggedoutwardly. More details of this preferred embodiment will become evidentwhen FIG. 4A is discussed below.

FIG. 3 illustrates some of the details of an embodiment of the coolingsystem for the reactor of the invention. The head of the reactor, 10,contains part of the circulation system (or recirculation system) forthe cooling medium, which may be provided by various liquids or gases aswould be recognized by one of ordinary skill in the art but forconvenience is typically water. In an embodiment, the top head will havetwo juxtaposed and interconnected compartments 35 and 37, respectively,the former from which the inlet 34 cooling water is distributed to thecooling tube or plurality of cooling tubes, and the latter to collectthe return water which exits through outlet 36. The plural cooling tubes(shown by reference to two cooling tubes 19A, 19B, for the sake ofclarity) may be arrayed as concentric bayonets-type tubes with the inletwater going down the center tubes 13A, 13B, and the outlet water comingup the outer concentric tube 17A, 17B, or vice versa. Although only twocooling tubes are shown in FIG. 3 for convenience of view, pluralcooling tubes may be arranged concentrically (or in some other geometricpattern or irregular pattern) inside vessel wall 21 of vessel 20 so asto form downcomer space 18 and riser column 15. Riser space 15 allowsthe gas and excess liquid to exit out the reactor through conduit 31 inreactor head 10 to outlet 30. A single opening (i.e., here the top ofthe riser column 15) near the top of the plurality of cooling tubes(e.g., corresponding to window 12 in FIG. 2A and FIG. 2B) which allowscirculation of the essentially gas-free or gas-depleted liquid down thedowncomer; connective webs or sheets 41A, 41B, are not shown in FIG. 3.The various parts of reactor head 10 may be welded, adhesivelyconnected, bolted, and the like (or combination thereof). Variousalternative or auxillary means of connections would be known to one ofordinary skill and may include the use of gaskets and the like.

The inner tube 13A passes through the outlet water compartment 36 and isopen to the top water compartment 35. The outer tube 17A may be weldedto the top head and is open to the outlet water compartment 36.

One of the unique advantages of the reactor system according to thepresent invention is that entire top head 10 comprising element 32 andinternal assembly comprising a plurality of cooling tubes illustrated bytubes 19A, 19B etc., can be lowered into the vertical shell duringconstruction as well as lifted out of the shell for any seriousmaintenance.

FIG. 4 illustrates an embodiment of the draft tube (16 in FIGS. 2A and2B) wherein the draft tube comprises plural cooling tubes formed bycooling tubes 19A, 19B, etc. FIG. 4A is a view taken of a preferredembodiment from the top portion of vessel 20 showing only the positionof the “dog-legged” tubes (above the connecting sheet or web 41A, 41B,etc. in FIG. 2B). In contrast, FIG. 4B is a view taken from the middleportion of the vessel 20 with the hemisperical end cap (11 in FIG. 2)removed, and shows the connective sheet or webs 41A, 41B, etc. betweeneach cooling tube.

In the arrangement shown in FIG. 4, the schematic view is bestunderstood first by reference to FIG. 4B. It will be understood that thearray of plural cooling tubes 19A, 19B, etc., can be in some othergeometric arrangement than that shown, such as in a squareconfiguration, and the like. Cooling tubes 19A, 19B, etc. may be weldedtogether or connected such as by sheet metal as shown by elements 41A,41B, etc., so that the combination of plural cooling tubes andconnective webs or sheets form the draft tube 16. The connective sheetsor webs 41A, 41B, etc., connect the plural cooling tubes from near thebottom portion of the draft tube to near the upper portion of the drafttube, the exact distance from the top and bottom being predetermined.The selection of distance between top and bottom is preferablyindependently determined. The determination may be made by experiment orwith the aid of computational fluid dynamic models using commerciallyavailable software, or a combination thereof. Using the reactordimensions provided elsewhere in the present disclosure (i.e., withrespect to vessel volume, height, diameter, etc.), it is sufficient butnot required that the distance of the top of the draft tube from the topof the vessel and the distance of the bottom of the draft tube from thebottom of the vessel be on the order of 1 to 3 meters, with about 2meters being preferred. Thus connected by the sheets or webs betweeneach cooling tube, plural cooling tubes 19A, 19B, etc. form the drafttube that separates riser column 15 downcomer column 18.

As mentioned the plural connecting elements, illustrated by sheets orwebs 41A and 41B in FIG. 4B, connect the plural cooling tubes 19A, 19B,etc., to a predetermined distance from the head of the reactor (32 inFIGS. 2B and 3) where the connecting web or sheet stops at saidpredetermined distance to provide at least one gap for recirculation.These gaps (12 and 14 in FIG. 2A and FIG. 2B) may be accentuated byaltering the geometry of the cooling tubes near the top, such asillustrated in FIG. 4A, where the cooling tubes each take an alternatinginward/outward “dog leg” to provide plural gaps, as discussed brieflyabove, thus providing or accentuating the gap between the individualcooling tubes 19A, 19B etc., and fluid communication between risercolumn 15 and downcomer column 18. Thus, cooling tube 19A is dog-leggedoutwardly with respect to the center line of the cooling tube (notlabelled in FIG. 4A) separating riser column 15 and downcomer column 18,while cooling tube 19B is dog-legged inwardly, and so on. The locationof the bends for the dog legs is a convenience place to discontinue theconnective plates or webs 41A, 41B, etc.

In consideration of the increased volume allowed in the reactoraccording to the invention, the exposure of bottom of the plural arrayof cooling tubes to the process pressures a significant buckling stressnot encountered in the design of the existing internal loop reactors.This may be addressed in various ways such as by the embodimentillustrated in FIG. 5.

In FIG. 5, the plural cooling tubes 19A, 19B, etc., are connected byplural webs or sheets, as discussed previously. In an embodiment, nearthe bottom of the draft tube, one or more of the tubes are cut short toallow the rod to pass through the draft tube. The other space on theother side has a wider sheet web to connect the rod to, as shown byconnective sheet or web 41A. Element 42A is intended to provide supportfor the draft tube 16 (FIG. 2) comprising plural cooling tubes 19A, 19B,etc. against the stresses referred to above. Support element 42A isadvantageously a flexible metal bar or rod. In an alternative, insteadof being connected to the web or sheet 41A it may be directly mated withthe cooling tube(s). The connection may be by welding, adhesive, or, asshown in the figure, by a hinge 40A. While support element 42A isadvantageously connected to the wall of vessel 20 at the point furthestlaterally from its connecting point to the draft tube 16 (FIG. 2), itmay be connected, instead or additionally) to another point on vessel20. As shown in FIG. 5, three support elements (one shown by thecombination of features 40A, 41A, 42A, the other equivalent elements notnumbered for ease of view) are used, but more or less (or no) supportelements may be used. Gaps in the circular array of plural cooling tubes19A, 19B, etc. are shown in the figure to allow for support elementshown individually by 42A. The riser column 15 and downcomer column 18in the figure are the same as shown in the other figures. Such gaps inthe array of cooling tubes 19A 19B etc. may be provided advantageouslyat the very bottom of the array simply by having the appropriate one ormore cooling tubes shortened slightly.

Numerous modifications in the reactor according to the invention may beenvisioned by one of ordinary skill in the art in possession of thepresent disclosure. For instance, as described above, the downcomer 18is fitted with a hemispherical cap, 11 in FIG. 2, in order to eliminatea dead zone observed in a cold flow unit which had a flat head. However,a different geometry may be optimal under other conditions.

In another embodiment, a circular baffle just above the top of the risermay help spread the plume of gas outward and avoid any possible masstransfer limitations in the top of the reactor.

In yet another embodiment, there is a conical slope for the underside ofthe top head 10 in FIG. 2 (or FIG. 3) to facilitate the flow of the gasrich layer and/or avoid stagnant bubbles under the head to the centraloutlet hole 30.

In still another embodiment, reactor 8 (by reference to FIG. 2) may havea second cooling means provided around vessel 20, such as shown byelement 3 in prior art FIG. 1.

It will be appreciated that in the case of plural cooling tubes thepattern formed by the cooling tubes may be other than as illustrated inFIGS. 4A, 4B, and 5, i.e., other than in a circular pattern. It may bein an irregular pattern, or some other regular pattern, such as asquare, rectangle, triangle, star pattern, and so on. FIG. 6 illustratesyet another alternative view of a cross-section of FIG. 2B acrossperspective line 4B, wherein plural cooling tubes 19A, 19B, etc., form a“zig-zag” pattern, connected by plural plates or webs illustrated by thesingle plate 41, to form the draft tube 16 separating riser column 15and downcomer column 18. FIG. 6 can be seen to be one of manyalternatives to the pattern shown by FIG. 4B.

In a preferred embodiment concerning construction and fabrication of thereactor according to the present invention, each individual cooling tubemay be extruded with one or more fins along the outer wall, which may beused to weld the individual cooling tubes into the draft tube so as toprovide the connective web or sheets represented by numerals 41A, 41B,etc.

It will be recognized by one of ordinary skill in the art in possessionof the present invention that in a preferred embodiment wherein thedraft tube comprises plural cooling tubes, a key mechanical feature ofthe present invention is that the conventional draft tube can be formedas an integral heat exchanger by welding individual heat exchanger tubestogether into a shape, such as a circle, which divides the riser anddowncomer columns. Without wishing to be bound by theory, among thebenefits provided by this approach are that by welding the integral finsfrom each cooling tube together, the welded assembly assumes asignificant stiffness much greater than any individual cooling tube.This stiffness allows the structure to withstand significant bucklingstresses which may arise in certain reactions, such as found in the OxoReaction, as discussed elsewhere herein. It is preferred that lateralsupports such as provided by the bar or rod indicated by 42A in FIG. 5be kept to a minimum, as such supports may detrimentally affect processpressure drop and provide locations for the deposition of material (suchas cobalt catalyst in the case of the conventional Oxo Reaction).

The reactor according to the present invention is particularly suitablefor carrying out an exothermic gas-liquid chemical reaction. The reactormay be provided in series or in parallel with other reactors of the sametype (e.g., internal loop reactors according to the invention oraccording to the prior art) or different types, such as one or moreexternal loop reactors in series with one or more reactors according tothe present invention. In the case where the reaction is endothermic theheat exchange medium is selected to be suitable for providing heat tothe reaction medium, which is within the skill of the ordinary artisan.

In a preferred embodiment, the reactor according to the presentinvention will be downstream of the main Oxo Reactors. In still morepreferred embodiments, up to about 10 to 15% of the overall Oxo reactionmay occur in the reactor according to the present invention when arrayedin series with plural additional external and/or internal loop reactors.Other configurations are possible, such as providing a reactor accordingto the present invention in a reactor array such as described in U.S.Pat. No. 5,763,678. However, it is to be understood that the reactoraccording to the present invention may function as a stand-alone reactorproviding 100% of the reaction product in a continuous or batchreaction.

Thus, in embodiments, the invention also relates to a process forcatalytic hydroformylation of an olefin feedstock by syn gas comprisingfeeding a stream comprising olefin and/or the product of ahydroformylation reaction having said olefin as a starting material,said stream comprising syn gas, to the inlet of a reactor and obtainingas a product of said reactor a stream comprising syn gas and saidproduct of a hydroformylation reaction, the improvement comprising aninternal loop reactor characterized by a plurality of cooling tubesforming the annulus between the riser and the downcomer path of saidinternal loop reactor. The reaction is also characterized by its verylarge volume, such as at least 15 cubic meters, or at least 20 cubicmeters, or at least 25 cubic meters, or more preferable at least 30cubic meters.

In a preferred embodiment, in place of or in addition to thermocouplesplaced at various points in the reactor, such as at elements 22A, 22B,22C, 22D, in FIG. 2A, it may be advantageous to use an analog continuoussignal from a standard flow switch (for example as supplied by numerousvendors such as Fluid Components International) to give a continuoustrend readout of the circulation velocity. In a preferred embodiment,such a switch would be adapted to be inserted into one of theaforementioned thermocouple nozzles.

In another preferred embodiment, flush mounting of the outlet nozzle tothe inside of the head to avoid gas pockets which could allow the onsetof Fischer Tropsch reactions.

Trade names used herein are indicated by a ™ symbol or ® symbol,indicating that the names may be protected by certain trademark rights,e.g., they may be registered trademarks in various jurisdictions.

All patents and patent applications, test procedures (such as ASTMmethods, UL methods, and the like), and other documents cited herein arefully incorporated by reference to the extent such disclosure is notinconsistent with this invention and for all jurisdictions in which suchincorporation is permitted.

When numerical lower limits and numerical upper limits are listedherein, ranges from any lower limit to any upper limit are contemplated.While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of theinvention. Accordingly, it is not intended that the scope of the claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty which reside in the present invention,including all features which would be treated as equivalents thereof bythose skilled in the art to which the invention pertains.

The invention has been described above with reference to numerousembodiments and specific examples. Many variations will suggestthemselves to those skilled in this art in light of the above detaileddescription. All such obvious variations are within the full intendedscope of the appended claims.

1. An apparatus for contacting two reactants to produce at least oneproduct, said apparatus comprising: a vertically disposed vessel havinga vertical axis, a sidewall, an upper portion and a lower portion; adraft tube comprising at least one heat exchange means, said draft tubeproviding a riser conduit within said draft tube and a downcomer conduitbetween said draft tube and said sidewall, said draft tube extendinginto the upper portion of said vessel and comprising at least oneopening in said upper portion so as to provide fluid flow communicationbetween the riser conduit and the downcomer conduit and extending intothe lower portion of said vessel and comprising at least one opening insaid lower portion so as to provide fluid flow communication between theriser conduit and the downcomer conduit; an inlet means for introducingsaid reactants; a gas outlet.
 2. The apparatus according to claim 1,wherein said draft tube comprises a plurality of cooling tubes.
 3. Theapparatus according to claim 1, wherein said upper portion of saidvessel comprises a vessel head comprising said gas outlet means, whereinsaid draft tube is suspended from said vessel head.
 4. The apparatusaccording to claim 3, wherein said vessel head is demountably engagedwith said vessel sidewall.
 5. The apparatus according to claim 1,wherein said draft tube is demountably engaged with said vessel sidewallin said lower portion of said vessel.
 6. The apparatus according toclaim 1, wherein the volume of said vessel is at least 20 cubic meters.7. A process for carrying out a reaction to form a product in theapparatus according to claim 1, which comprises: introducing at leastone liquid reactant and at least one gaseous reactant through said inletmeans so that said at least one liquid reactant and at least one gaseousreactant travel generally upward in said riser conduit of said drafttube comprising at least one heat exchange means and reacting said atleast one liquid reactant and said at least one gaseous reactant to formsaid at least one product while said reacting produces or consumes heat,said heat being exchanged with said heat exchange means; passing atleast one gas out of said apparatus through said gas outlet; passing afluid comprising said at least one liquid reactant and/or said at leastone product through said at least one opening in said upper portion andthen in a generally downward direction in said downcomer conduit; andisolating said product.
 8. The process of claim 7, wherein said heatexchange means comprises at least one cooling tube.
 9. The process ofclaim 7, wherein said heat exchange means comprises a plurality ofcooling tubes.
 10. The process of claim 7, wherein said reaction is theOxo Reaction.
 11. In a process for catalytic hydroformylation of anolefin feedstock by syn gas comprising feeding a stream comprisingolefin and/or the product of a hydroformylation reaction having saidolefin as a starting material, said stream comprising syn gas, to theinlet of an internal loop reactor and obtaining as a product of saidreactor a stream comprising syn gas and said product of ahydroformylation reaction, the improvement comprising a heat exchangerforming the draft tube between the riser column and the downcomer columnof said internal loop reactor.
 12. The process of claim 11, wherein thevolume of said internal loop reactor is at least 20 cubic meters. 13.The process of claim 11, wherein said heat exchanger comprises aplurality of cooling tubes.
 14. An internal loop reactor characterizedby a plurality of cooling tubes forming a draft tube between a risercolumn and a downcomer column of said internal loop reactor.
 15. Thereactor of claim 14, wherein said reactor is further characterized by aremovable top capping said reactor, and wherein the plurality of coolingtubes are attached to said top.
 16. The reactor of claim 14, wherein atleast a portion of the bottom of said draft tube comprising a pluralityof cooling tubes is attached to the wall of said internal loop reactor.17. The reactor of claim 4, wherein the draft tube provided by saidplurality of cooling tubes forms a first concentric circle at the bottomportion of said draft tube but wherein the top of said annulus isdefined by two concentric circles defined by alternating the connectionof the plurality of cooling tubes to said top so that said twoconcentric circles are characterized, respectively, by one having alarger radius than said first concentric circle and one having a smallerradius than said first concentric circle.